Ferrule holding structure for optical connector component

ABSTRACT

Disclosed is an optical connector component  31  comprising a ferrule  2  for receiving an end portion of a core optical fiber of a fiber optic cable, a flange  32  mounted on the peripheral of the ferrule  2,  and a one-piece plug frame  33  for floatingly supporting the ferrule  2  having the flange  32  mounted thereon. The flange  32  and the plug frame  33  are provided with respective engagement portions  37, 50  that are mutually engaged. The flange  32  has such resiliency that it is reduced in diameter by a radial and inward force exerted through the engagement portions  37, 50  when the ferrule  2  is inserted into the plug frame  33  from one end thereof and the flange  32  is restored to the original condition present before the insertion when the engagement portions  37, 50  are mutually engaged.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ferrule holding structure for anoptical connector component for use in connection between fiber opticcables.

2. Description of the Related Art

In general, in an optical communication system, several types of opticalconnector components have been used for detachably connecting betweenone fiber optic cable and another fiber optic cable or other opticaldevice. One example of such optical connector components is an opticalattenuator that is disclosed in TOKKOHEI No. 5-45924. Such opticalattenuator is designed to have optical connectors mounted on both sidesthereof so that an optical signal is relayed and attenuated betweenthose optical connectors.

One such conventional type attenuator 1 is illustrated in FIG. 4.Referring to this figure, the optical attenuator 1 includes a ferrule 2for receiving a core optical fiber at the center thereof, a connectionsleeve 3 for an attenuation film 61 affixed to an outer middle portionof the ferrule 2, a split sleeve 4 affixed to an outer rear end portionof the ferrule 2, a first plug frame 5 for surrounding and holding afront end portion of the ferrule 2, a second plug frame 6 forsurrounding and holding an opposite rear end portion of the ferrule 2,and a housing member 7 for accommodating the first and second plugframes 5 and 6.

The ferrule 2 is made of some ceramic material such as zirconia and hasan axially elongated cylindrical form on which the attenuation film 61is deposited for attenuating the passage of light.

The connection sleeve 3 is made of some metal material such as copperalloy in the form of a hollow cylinder that is affixed to the ferrule 2with an adhesive. A flange 8 is affixed on an outer peripheral of theferrule 2 adjacent a front end of the sleeve 3. The flange 8 is made ofmetal and has predetermined number of grooves (not shown) formed on anouter surface thereof.

The split sleeve 4 is made of zirconia, for example, in the form of ahollow cylinder and is axially split to provide resiliency. The splitsleeve 4 has a front end surface that is contact with the rear endsurface of the connection sleeve 3, and an opposite rear end surfacethat is backwardly projected beyond the rear end surface of the ferrule2.

The first plug frame 5 is made of some plastic material, for example,and it is generally in the form of a cubic in which a cylindrical cavity9 is axially formed. An inner brim 10 is formed at the inner centerportion of the first plug frame 5 and has keys provided at the rear endportion thereof in corresponding to the grooves in the flange 8.Thereby, the ferrule 2 having the connection sleeve 3 mounted thereon isprevented from falling off the front end of the attenuator 1. A firstengagement portion 12 is formed on and projected from an outer surfaceof the first plug frame 5, and a protrusion 13 is formed on the rearportion of the first engagement portion 12. In addition, latch holes 14are formed at positions opposite to each other on the rear portion ofthe first plug frame 5, and elongated cutouts (not shown) are alsoformed at another positions opposite to each other to extend from therear end of the first plug frame 5.

The second plug frame 6 is made of some plastic material, for example,and includes, a cylindrical holding portion 16 in axial direction and apair of thin plate-like resiliently deformable portions 17 that extendin cantilevered manner from the middle portion of the holding portion 16toward the rear end of the attenuator 1. Each of the deformable portions17 has its rear end portion inwardly projected to form a secondengagement portion 18. The holding portion 16 has its outer surface onwhich latch projections 19 are formed at the positions corresponding tothe latch holes 14, and its inner surface on which a shoulder 20 isformed at the middle portion thereof. The holding portion 16 furtherincludes an inwardly projecting fall-off prevention portion 21 formed onthe rear end portion thereof for preventing the ferrule 2 fixed to thesplit sleeve 4 from falling off the holding portion 16.

The housing member 7 is made of stainless steel, for example, andincludes a front end portion 22 that is mated with an adapter (notshown) and a rear end portion 23 with which a plug (not shown) is mated.The front end portion 22 has such width that is smaller than that of therear end portion 23 so that there is a difference in width producedtherebetween. An opening 24 is provided on each of both sidewalls of thefront end portion 22. Accordingly the first engagement portion 12 andthe protrusion 13 may cause an axial floating movement along theopenings 24. In addition, a key projection 25 is formed on an outersurface of the front end portion 22, and the corresponding guide recess26 is formed in the sidewall of the rear end portion 23 so that itaxially extends from the rear end thereof.

Now, the process of assembling the prior art optical attenuator 1 havingthe configuration as above will be described.

The connection sleeve 3 is affixed to the ferrule 2 with an adhesive.Then, the flange 8 is affixed so that it is contact with the front endsurface of the connection sleeve 3. The split sleeve 4 is press-fittedso that it is contact with the rear end surface of the connection sleeve3. Thereafter, the front end portion of the ferrule 2 having theconnection sleeve 3, the split sleeve 4 and the flange 8 mounted thereonis inserted into the cavity 9 of the first plug frame 5 from the rearside thereof In this connection, the groove (not shown) on the flange 8is mated with the key 11 of the first plug frame 5 so that the flange 8abuts the brim 10. Then, the second plug frame 6 is inserted into thefirst plug frame 5 in such manner that the holding portion 16 of thesecond plug frame 6 surrounds the rear end portion of the split sleeve4. Thereafter, the second plug frame 6 is further inserted until thelatch projection 19 snaps into the latch hole 14 upon which the secondplug frame 6 is coupled to the first plug frame 5. In this condition theferrule 2 may floatingly be moved in the axial direction between theinner brim 10 of the first plug frame 5 and the shoulder 20 of thesecond plug frame 6. Finally the first and second plug frames 5 and 6coupled together are inserted into the housing member 7 from the rearside thereof until the first engagement portion 12 and the protrusion 13become received in the opening 24. Accordingly, the first and secondplug frames 5 and 6 are held in the housing member 7, but they mayfloatingly be moved in the axial direction.

The optical attenuator 1 that is assembled in the manner as above isthen connected as follows: When the front end portion 22 is mated withthe adapter (not shown) so that the key projection 25 is received in theguide recess (not shown) of the adapter, then the first engagementportion 12 is engaged with the adapter. On the other hand, when the rearend portion 23 is mated with the plug (not shown) so that the keyprojection (not shown) of the plug is received in the guide recess 26,then the second engagement portion 18 is engaged with the plug. As theresult, the plug is connected with the adapter through the opticalattenuator 1.

However, the prior art optical connector components such as thoseincluding the optical attenuator 1 as described above are generallydefective in that they need great number of parts and assembling steps,and involves many laborious works because of the sleeve 3 and the flange8 made of metal. In addition, they are difficult to reduce themanufacturing cost.

Because an adhesive is used for affixing the connection sleeve 3 to theferrule 2, any excessive amount of adhesive that has come out of the endof the connection sleeve 3 flows into between connection sleeve 3 andthe split sleeve 4 or the flange 8, which may cause deterioration inprecision of the length between the flange 8 and the split sleeve 4.Therefore, it is difficult to improve in precision of size and yield ofthe product in the prior art.

In view of the above an object of the present invention is to provide aferrule holding structure that can reduce the number of parts andassembling steps, improve in precision of size and yield of the product,and reduce the manufacturing cost of the product.

SUMMARY OF THE INVENTION

To attain such object the present invention provides an opticalconnector component comprising a ferrule for receiving an end portion ofa core optical fiber of a fiber optic cable, a flange mounted on theperipheral of the ferrule, and a one-piece plug frame for floatinglysupporting the ferrule having the flange mounted thereon, in which theflange and the plug frame are provided with respective engagementportions that are mutually engaged, and in which the flange has suchresiliency that it is reduced in diameter by a radial and inward forceexerted through the engagement portions when the ferrule is insertedinto the plug frame from one end thereof and the flange is restored tothe original condition present before the insertion when the engagementportions are mutually engaged.

Preferably the flange is provided with an adhesive injection hole in theperipheral wall thereof and an enlarged diameter recess portion at oneend thereof, and when an adhesive is injected into the adhesiveinjection hole after the flange is mounted on the ferrule, then theadhesive flows between the flange and the ferrule and reaches theenlarged diameter recess portion.

Furthermore, a clearance is produced between the flange and the ferrule,and when the ferrule having the flange mounted thereon is inserted intothe plug frame from one end thereof, the flange is reduced in diameterdue to the presence of the clearance. The flange is made of resinmaterial.

Such construction of the present invention allows reduction in number ofparts and assembling steps for the optical connector component,facilitated assembly works, improvement in precision of size, andreduction of manufacturing cost. In addition, there is substantially nopossibility that an adhesive used for affixing the flange to the ferrulecomes out of the end of the flange, which is effective to improve inprecision of size and yield of the product.

BRIEF DESCRIPTION OF THE INVENTION

Now, the present invention will be described with reference to theaccompanying drawings, in which:

FIG. 1 is an enlarged view of an optical attenuator according to anembodiment of the present invention, illustrating an upper half of theattenuator in cross section;

FIG. 2 is an enlarged view showing a flange according to the embodimentof the present invention partially in cross section;

FIG. 3 is an enlarged view of a plug frame according to the embodimentof the present invention, illustrating an upper half of the plug framein cross section; and

FIG. 4 is an enlarged view of an optical attenuator in the prior art,illustrating an upper half of the attenuator in cross section.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described in more detail with reference toFIGS. 1 to 3 illustrating an optical attenuator 31 constructed accordingan embodiment of the present invention. For the purpose ofsimplification, the parts corresponding to that of the prior art opticalattenuator 1 are indicated by the same reference numbers and thedescription regarding such parts are omitted.

FIG. 1 is an enlarged view of an optical attenuator 31 according to anembodiment of the present invention, illustrating an upper half of theattenuator in cross section. The optical attenuator 31 includes aferrule 2 having an attenuation film or an attenuation fiber providedthereon, a flange 32 affixed to an outer peripheral at the middleportion of the ferrule 2, a split sleeve 4, a plug frame 33 forsupporting the ferrule 2 on which the flange 32 and the split sleeve 4are affixed, and a housing member 7.

FIG. 2 is an enlarged view showing the flange 32 partially in crosssection. The flange 32 is made of plastic material in the form of acylinder having the wall thickness greater than that of the split sleeve4. A press-fit portion 34 having the minimum inner diameter is formed inthe middle portion of the flange 32. The ferrule 2 is press-fitted tothis press-fit portion 34. The flange 32 further includes a deformableportion 35 positioned near the front end thereof and an adhesion portion36 positioned near the rear end thereof The deformable portion 35 andthe adhesion portion 36 have respective inner diameter greater than thatof the outer diameter of the ferrule 2.

The deformable portion 35 has the predetermined number (two in FIG. 2)of engagement projections 37 formed on the outer surface thereof. Eachof the engagement projections 37 has a tapered portion at the rear side.The deformable portion 35 further has the predetermined number (forexample, four) of axial slits 38 formed in the peripheral wall thereof.The axial slit 38 is in the form of a triangle whose acute angled apexis pointed to rear side. A front end 39 of the deformable portion 35 hasthe maximum inner diameter so that there is a tapered surface 40produced between the front end 39 and the press-fit portion 34. When theflange 32 is mounted to the ferrule 2, a clearance 60 is producedbetween the deformable portion 35 and the ferrule 2. The adhesionportion 36 has the predetermined number (two in FIG. 2) of circularadhesive injection holes 41 formed in the peripheral wall thereof. Anenlarged diameter recess portion 42 is formed on an inner surface of theflange 32 at the rear end thereof When the flange 32 is mounted to theferrule 2, a clearance 57 is produced between the adhesion portion 36and the ferrule 2.

FIG. 3 is an enlarged view of the plug frame 33, illustrating an upperhalf of the plug frame in cross section. The plug frame 33 is made ofplastic material, for example, and includes a cylindrical holdingportion 43 in axial direction and a pair of resiliently deformableportions 44 that extend in cantilevered manner from the rear end portionof the holding portion 43 toward the rear side of the attenuator 31. Theholding portion 43 is designed to floatingly hold the ferrule 2 havingthe flange 32 and the split sleeve 4 mounted thereon. The holdingportion 43 is integral with the resiliently deformable portions 44.

The holding portion 43 is divided into the following sections dependingon the wall thickness: a first thin wall section 45; a middle wallthickness section 46; a thick wall section 47; and a second thin wallsection 48. A first engagement portion 49 is formed on the outer surfaceof the first thin wall section 45, a square engagement hole 50 is formedin the middle wall thickness section 46, and a protrusion 51 is formedon the outer surface near the engagement hole 50. The outer surface ofthe holding portion 43 between the first thin wall section 45 and themiddle wall thickness section 46, and the front side of the protrusion51 are outwardly slanted. The inner surface of the holding portion 43 isprovided with a first shoulder portion 52 between the first thin wallsection 45 and the middle wall thickness section 46, and a secondshoulder portion 53 between the middle wall thickness section 46 and thethick wall section 47. The inner diameter of the holding portion 43 isreduced stepwise from the first thin wall section 45 toward rear side ofthe optical attenuator 31. An inwardly projecting fall-off preventionportion 54 is formed on the rear end of the second thin wall section 48.The fall-off prevention portion 54 has its inner diameter that issmaller than the outer diameter of the split sleeve 4, but greater thanthe outer diameter of the ferrule 2. The length between the secondshoulder portion 53 and the fall-off prevention portion 54 is greaterthan that of the split sleeve 4. Each of the pair of resilientlydeformable portions 44 includes a resilient arm 55 extending incantilevered manner from the rear end portion of the deformable portion44 toward the front side of the attenuator 31. The resilient arm 55 isprovided with a second inwardly projecting engagement portion 56 at thefront end thereof. Because the first engagement portion 49 and thesecond engagement portion 56 are formed on one and same plug frame 33,it becomes easy to control the length between the first engagementportion 49 and the second engagement portion 56 and to allow improvementin precision of the size.

Next, the process of assembling the optical attenuator 31 will bedescribed in more detail.

The ferrule 2 is press-fit to the flange 32 and is held in the press-fitportion 34 of the flange 32. Then the predetermined amount of adhesiveis injected via the adhesive injection hole 41 into the flange 32. Theadhesive fills the clearance 57 and reaches the enlarged diameter recessportion 42. Because the enlarged diameter recess portion 42 has theinner diameter that is greater than that of the remaining portion of theadhesion portion 36, there is substantially no possibility that theadhesive that has reached the enlarged diameter recess portion 42 wouldleak to anywhere at the rear side thereof.

Thereafter, the ferrule 2 having the flange 32 mounted thereon isinserted into the split sleeve 4. The front end surface of the splitsleeve 4 abuts the rear end surface of the flange 32 and the rear endportion of the split sleeve 4 backwardly projects beyond the rear end ofthe ferrule 2. Because of the wall thickness of the flange 32 greaterthan that of the split sleeve 4, a shoulder portion 58 is providedbetween the flange 32 and the split sleeve 4. Because of no possibilitythat the adhesive would be leaked from the rear end of the flange 32, asdescribed above, the split sleeve 4 intimately abuts the flange 32without any clearance therebetween. Accordingly the fixed length canalways be assured between the front end surface of the flange 32 and therear end surface of the split sleeve 4, which allows improvement inprecision of size of the product.

Next, the ferrule 2 having the flange 32 and the split sleeve 4 mountedthereon is inserted into the holding portion 43 of the plug frame 33from the front side thereof, as described earlier. The engagementprojection 37 of the flange 32 has the tapered outer surface formed atthe rear side thereof, and therefore, it is smoothly slid along theinner surface of the first thin wall section 45 of the plug frame 33 toapply a radial and inward force to the deformable portion 35. Becausethere is the clearance 60 present between the deformable portion 35 andthe ferrule 2, and the predetermined number of the slits 38 formed inthe flange 32, the deformable portion 38 is gradually reduced indiameter. As the ferrule 2 is further inserted into the holding portion43, the engagement projection 37 abuts the inner surface of the middlewall thickness section 46, after passing through the first shoulderportion 52. Because the middle wall thickness section 46 has its innerdiameter that is smaller than that of the first thin wall section 45,the deformable portion 35 is further reduced in diameter. Thereafter,the engagement projection 37 snaps into the engagement hole 50 and thedeformable portion 35 restores the original condition where it wasbefore insertion. Now, the ferrule 2 having the flange 32 and the splitsleeve 4 mounted thereon is floatingly supported in the holding portion43 of the plug frame 33. In this condition any movement of the ferrule 2in the direction toward the front side is restricted due to the abutmentbetween the front end surface of the engagement projection 37 and afront side surface 59 of the engagement hole 50. On the other hand, anymovement of the ferrule 2 in the opposite direction toward the rear sideis restricted due to the abutment between the shoulder portion 58 andthe second shoulder portion 53 because of the length between the secondshoulder portion 53 and the fall-off prevention means 54 greater thanthat of the split sleeve 4. Accordingly, in view of the fact that thefront side surface 59 of the engagement hole 50 and the second shoulderportion 53 are formed on one and same plug frame 33, the lengththerebetween, or in other word, an extent of floating movement, caneasily be controlled, and consequently, improvement in precision of sizecan be attained. Furthermore, there is substantially no possibility thatthe split sleeve 4 is broken or damaged when it is collided to thefall-off prevention means 54.

Next, the plug frame 33 having the ferrule 2 contained therein isinserted into the housing member 7 from the rear side thereof. The firstengagement portion 49 and the protrusion 51 are received in the opening24 so that the plug frame 33 is axially floatingly supported in thehousing member 7.

In the embodiment as above, the optical attenuator has been described byway of an example. The present invention, however, is not limited tosuch optical attenuator, but may applied to any other optical connectorcomponents such as a filter, a terminator, etc.

The flange 32 and the plug frame 33 may include any other mutualengagement portion than that described above. For example, as opposed tothe embodiment as described above, the engagement projection 37 may beformed on the plug frame 33 and the engagement hole 50 may be formed inthe flange 32.

In addition, the present invention may be configured in such manner thatthe ferrule 2 having the flange 32 mounted thereon is inserted into theplug frame 33 from the rear side thereof. Alternatively the flange 32may be formed in which the deformable portion 35 is positioned at therear side to the press-fit portion 34 and the adhesion portion 36 ispositioned at the front side to the press-fit portion 34.

It is apparent from the forgoing that a plug frame is configured as aone-piece component, a flange is made of resin material and has anengagement portion formed thereon, and a ferrule is held in the plugframe simply by inserting the ferrule having the flange mounted thereoninto the plug frame from one side thereof. Therefore, it is possible toreduce the number of component parts and assembling steps, to simplifythe assembling operations and to reduce the manufacturing cost.

Furthermore, because of an enlarged diameter recess portion formed atthe end of the flange, there is substantially no possibility that anadhesive used for affixing the flange to the ferrule comes out of theend of the flange, which allows improvement in precision of size andyield of the product.

What is claimed is:
 1. A ferrule holding structure of an opticalconnector component comprising a ferrule for receiving an end portion ofa core optical fiber of a fiber optic cable, a flange mounted on theperipheral at a middle portion of the ferrule, and a one-piece plugframe for floatingly supporting the ferrule having the flange mountedthereon, a the ferrule holding structure comprising the flange and theplug frame, wherein: each of the flange and the plug frame is providedwith respective engagement portions, wherein the engagement portions ofthe flange and the engagement portions of the plug frame that aremutually engaged when the ferrule is fully inserted in the plug frame;the flange has such resiliency that it is reduced in diameter by aradial and inward force exerted through the engagement portions of theflange as the ferrule is inserted into the plug frame from one endthereof and the flange is restored to the original condition presentbefore the insertion when the respective engagement portions of theflange and the plug frame are mutually engaged: and the flange has anadhesion portion, a peripheral wall of the flange defining an adhesiveinjection hole therethrough in said adhesion portion, and said flangebeing sized to form a first clearance between the adhesion portion ofthe flange and the ferrule.
 2. The ferrule holding structure accordingto claim 1 in which a second clearance is produced between the flangeand the ferrule in an area proximate the engagement portions of theflange, and when the ferrule having the flange mounted thereon isinserted into the plug frame from one end thereof, the flange is reducedin diameter due to the presence of the second clearance.
 3. The ferruleholding structure according to claim 2 in which the flange is made ofresin material.
 4. A ferrule holding structure of an optical connectorcomponent comprising a ferrule for receiving an end portion of a coreoptical fiber of a fiber optic cable, a flange mounted on the peripheralof the ferrule, and a one-piece plug frame for floatingly supporting theferrule having the flange mounted thereon, the ferrule holding structurecomprising the flange and the plug frame, wherein: each of the flangeand the plug frame is provided with respective engagement portions,wherein the engagement portions of the flange and the engagementportions of the plug frame are mutually engaged when the ferrule isfully inserted in the plug frame, the flange has such resiliency that itis reduced in diameter by a radial and inward force exerted through theengagement portions of the flange as the ferrule is inserted into theplug frame from one end thereof, and the flange is restored to theoriginal condition present before the insertion when the respectiveengagement portions of the flange and the plug frame are mutuallyengaged, and the flange is provided with an adhesive injection hole inthe peripheral wall thereof and an enlarged diameter recess portion atone end thereof, and when an adhesive is injected into the adhesiveinjection hole after the flange is mounted on the ferrule, then theadhesive flows between the flange and the ferrule and reaches theenlarged diameter recess portion.
 5. The ferrule holding structureaccording to claim 4 in which a clearance is produced between the flangeand the ferrule, and when the ferrule having the flange mounted thereonis inserted into the plug frame from one end thereof, the flange isreduced in diameter due to the presence of the clearance.
 6. The ferruleholding structure according to claim 5 in which the flange is made ofresin material.